Unsteady flow and excitation characteristics in a vortex pump

The impeller in vortex pumps is installed at the side of the volute, which causes the flow instability and vibration. This study employs the Renormalization Group k-epsilon (RNG k-ε) turbulence model to investigate the unsteady flow and excitation characteristics within a vortex pump under various flow rates. The results show that increasing the flow rate reduces the low-pressure area in the vaneless chamber, with flow instability primarily occurring in the middle of the vaneless chamber and intensifying with higher flow rate. Pressure pulsation within the vaneless chamber at nominal flow rate is driven by periodic changes in the vortex structure, occurring at approximately twice the shaft frequency (96Hz). As the impeller rotates, pulsation energy propagates from the vaneless chamber to the tongue and outlet. With increasing flow rates, variations of inlet axial flow velocity cause the rise in pressure pulsation in the vaneless chamber. At high flow rate, pressure pulsation in the vaneless chamber increases tenfold compared to low flow rate. The pressure pulsation at the tongue is significantly smaller than that in the vaneless chamber. The rise in pressure pulsation with increasing flow rates is attributed to the displacement of the circulation flow position towards the tongue.